Optical fiber connector

ABSTRACT

Disclosed is an optical fiber connector that comprises two right capillary cylinders or &#34;plugs&#34;, an alignment sleeve that contactingly maintains the plugs in substantially fixed relative relation, and means for maintaining the plugs in substantially fixed relative axial relation. Connectors according to the invention can have very low insertion loss, are easily field-installed, can be easily and relatively inexpensively manufactured, and are useful for single mode as well as for multimode fiber applications. In a preferred embodiment the connector takes the form of the ST® connector.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of our copending application Ser. No. 527,341,filed on Aug. 29, 1983, now U.S. Pat. No. 4,850,670.

1. Field of the Invention

This invention pertains to splices and connectors for optical fiber.

2. Background of the Invention

Optical fiber connectors and splices (hereinafter referred tocollectively as "connectors") are an essential part of substantially anyoptical fiber communication system. For instance, connectors may be usedto join segments of fiber into longer lengths, or to connect fiber toactive devices such as radiation sources, detectors, or repeaters, or topassive devices such as switches or attenuators.

The task of an optical fiber connector is twofold. First, it must coupleor join two optical fibers with minimum insertion loss. Second, it mustprovide mechanical stability and protection to the junction in itsworking environment. Achieving low insertion loss in coupling two fibersis generally a function of the alignment of the fiber ends, the width ofthe gap between the ends, and the optical surface condition of either orboth ends. Stability and junction protection is generally a function ofconnector design, e.g., minimization of differential thermal expansioneffects.

The prior art knows many approaches to achieving fiber alignment. Amongthem are V-grooves, three-rod containment, resilient ferrules,elastomeric bushings, jewel bushings, conical nose/conical bushing, andprecision ferrule/precision bushing devices. A discussion of some priorart connectors can be found, for instance, in R. Schultz, Proceedings ofthe Optical Fiber Conference, Los Angeles, (September 1982), pp.165-170.

For example, U.S. Pat. No. 4,205,897, issued June 3, 1980 to W. C.Stankos, for "Fiber Optic Connector for Single Fiber," discloses aconnector and coupling assembly for coupling a single pair of opticalfibers in which the respective fibers are secured in identical metallicconnector pins inserted into an alignment sleeve having a precisionaxial aperture. As a further example, U.S. Pat. No. 4,135,781, issuedJan. 23, 1979, to J. D. Archer, for "Optical Fiber Termination",discloses a method for terminating an optical fiber by means of aconnector by pushing the plastic-clad optical fiber into a heaterferrule containing a pierced watch bearing jewel, so as to force thebare fiber through the aperture in the jewel, then fusing the protrudingfiber end, and polishing the fused fiber end flush with the jewelsurface.

A further example of prior art connectors is described by R. Schultz(op. cit.). (See also Design News, Dec. 6, 1982, pp. 60-61.) Theconnector described therein comprises a glass tube, factory-bonded to ametallic connector body assembly. Stripped fiber is threaded through thebore of the glass tube, and held in place therein by means of UV-curableadhesive. A metal ferrule is slipped over the length of fiber juttingfrom the glass tube/body assembly and held in place by means of acoupling ring. The fiber end protruding from the slightly concaveferrule surface is scribed and broken close to the ferrule. The ferrulecan then be inserted without further processing into a mating bushing ofan appropriate adapter or receptacle to complete a connection.

Prior art optical fiber connectors typically contain one or moreprecision machined parts and are therefore relatively costly items.Whereas this may be acceptable for some applications, e.g., in trunklines, in other cases the price of connectors of the prior art typemight constitute a significant fraction of the total installation price.An example of such an installation is considered to be a local areanetwork (LAN), which usually would require many, perhaps hundreds, offiber connectors.

A further and very important consideration is the relative ease of fieldinstallation of an optical fiber connector, since a complicated andlengthy installation procedure may significantly affect the installedprice of a multiconnector optical fiber network. It is thus desirablethat the installation of a connector not only be accomplishable within arelatively short period of time but also that the installation notrequire special skills, or manipulations not easily carried out in thefield.

It is thus evident that an optical fiber connector whose parts can beeasily and inexpensively produced, which can be quickly and simplyinstalled by relatively unskilled personnel in the field, and which,furthermore, is compatible with all environmental conditions it islikely to encounter, and which has extremely low insertion loss, wouldbe of great commercial importance. This application discloses such anoptical fiber connector.

SUMMARY OF THE INVENTION

The inventive optical fiber connector is a device for abuttingly joiningone optical fiber to another optical fiber. The connectors can assume avariety of forms, including the form of multichannel connectors, and isuseful for connecting single mode fiber as well as for connectingmultimode fiber. Furthermore, the principle of the inventive device canbe embodied in other fiber-optic devices, e.g., a variable attenuator, afiber-to-fiber switch, or a simple in-line optical fiber.

A complete connector according to the invention comprises two drawncapillary glass right circular cylinders, each cylinder having a "free"end face, alignment means, acting on the outside surfaces of thecylinders, for maintaining the cylinders in radially fixed relation toeach other, and axial spring means for maintaining the free end faces ofthe cylinders in fixed axial relation to each other.

A connection is made by inserting the bared end of a fiber into thecapillary bore of a cylinder, threading it through the length of thecylinder, followed by fixing the fiber in the capillary bore byappropriate (e.g., adhesive) means, and preparing the fiber end to beflush with the free end face of the cylinder, e.g., by grinding and/orpolishing. Two similarly prepared cylinders are then maintained inradially and axially fixed relationship by the above-mentioned means,such as to permit at least a substantial fraction of electromagneticradiation emitted from one fiber end to couple into the second fiberend.

The inventive connector contains only one type of precision element,namely, the two drawn capillary glass cylinders. This element can beeasily and cheaply manufactured to within close tolerances. The fiberpreferably fits relatively loosely into the capillary bore (diameterdifference preferably between about 0.5 μm and about 5 μm), since theadhesive material typically filling the space between fiber andcapillary wall apparently can exert a dynamic centering effect on thefiber during fiber insertion, resulting in an accurately concentricassembly.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an exemplary as-drawn and cut glass capillary cylinder;

FIG. 2 depicts an exemplary chamfered and insertion-coned glasscapillary cylinder;

FIG. 3 gives in exploded view the parts of a connector according to theinvention;

FIG. 4 shows in partial cross-section an assembled exemplary connectoraccording to the invention;

FIG. 5 illustrates a further exemplary embodiment of the invention,namely, a feed-through connector of the twist-and-lock type;

FIG. 6 gives exemplary experimentally obtained data on connectorinsertion loss vs. cylinder end face separation;

FIG. 7 shows schematically an embodiment of the invention adapted tofunction as a variable attenuator; and

FIG. 8 shows schematically an embodiment of the invention adapted tofunction as a fiber-to-fiber switch.

Like features in the drawings are identified by like numerals.

DETAILED DESCRIPTION

One of the central aspects of this invention is the use of drawn glasscapillary cylinders as the sole precision elements in a optical fiberconnector. Methods for "drawing down" tubular glass preforms, to therebyproduce a reduced-cross-section replica of the preform, as well known inthe art and need no detailed exposition. It will, for instance, bereadily apparent to those skilled in the art that the preform has tohave substantially the same ratio of outer to inner diameter as thecapillary cylinder. To achieve the required dimensions on the finishedpart, it may be necessary to change the outside diameter of an availableglass tube by grinding, or to employ other appropriate procedures forachieving the required ratio in the preform.

A critical parameter of a glass capillary cylinder for use in aconnector according to the invention is the bore eccentricity, whichshould be as small as possible, typically less than about 5 percent,preferably less than 2 percent. Bore eccentricity herein is defined asΔ/a, where a is the capillary bore radius, and Δ the concentricityerror, i.e., the amount by which the bore axis is shifted from thecylinder axis.

FIG. 1 shows in cross-section an exemplary glass capillary cylindersubstantially as drawn and then cut from the drawn capillary tube.Capillary cylinder 10 has outer diameter 2A, and substantiallyconcentric bore 11 of diameter 2a. Exemplary approximate dimensions are2A=2.5 mm, 2a=0.13 mm, and length about 12.5 mm. The cylinder canconsist of any appropriate glass, e.g., PYREX, quartz, borosilicate orsoda-lime glass.

An exemplary capillary cylinder suitable for incorporation into aconnector according to the invention is shown in cross-section in FIG.2. End faces 20 and 21 are prepared, e.g., by cutting or grinding, to besubstantially perpendicular to the cylinder axis. Face 21, which is tobe the "free" end face of the cylinder, in particular, should beaccurately perpendicular, and also should have good surface finish.Fiber insertion into the bore is aided by means of fiber entry cone 22.Chamfer 23, as well as cone 22, can be produced by any appropriatemeans, e.g., by grinding, etching, or fire polishing. Presence of afiber entry cone is not always necessary in the glass cylinder, sinceother ways of ensuring easy fiber into the capillary bore exist, e.g.,an entry cone in the bore of the connector base.

A complete fiber connection according to the invention comprises, inaddition to the two drawn glass capillary cylinders (which are notnecessarily of equal length, but typically and closely matched in OD andbore diameter), alignment means for maintaining the cylinderssubstantially radially fixed with respect to each other. Although allmeans for achieving such alignment are intended to be within the scopeof the invention, we have found that a simple alignment sleeve, i.e., asplit, thin-walled cylinder made of metal (e.g., phosphor bronze, steel)or any other appropriate material (e.g., plastic), performs thisfunction well.

An inventive connection also comprises means, typically comprising anelastically deformable body, e.g., a spring, for maintaining the twoglass cylinders in axially fixed relation with each other. This relationis, at least in the case of a simple connector, a contacting one (withor without the presence of a thin layer of index-matching materialbetween the free end faces). In this case, the free end faces of the twocylinders are maintained in contacting relationship by means of anaxially applied force. For instance, we have found that a simplemounting clip, made of phosphor bronze, steel, plastic, or any otherappropriate material, can perform this function.

FIG. 3 shows, in exploded view, parts of a simple connector according tothe invention, with glass cylinders 10 to be held in radially fixedrelation by split alignment sleeve 30, and in axially fixed relation, inthis case contacting relation, by mounting clip 31. Connector bases 32serve, inter alia, to hold (in bore 34) the coated fiber in fixedrelationship with respect to the connector, thereby reducing stress onthe bare fiber end, and to provide means for applying theaxial-position-maintaining force, e.g., shoulder 33. The connector basetypically is a low precision part, e.g., an aluminum screw machine part,or an injection molded plastic part. However, the base advantageouslyprovides centering means for the coated fiber. This can be achieved, forinstance, by providing a relatively close fit between the coated fiberand the bore of the base.

A connector according to the invention can be assembled by, forinstance, inserting an appropriately prepared drawn glass cylinder intoa connector base, and attaching it permanently thereto, e.g., by meansof epoxy, press-fit, or UV-curable adhesive (e.g., a diacrylate adhesivesuch as ACE 7515, manufactured by American Chemical EngineeringCompany). In the latter case, the base advantageously is fabricated fromUV-transmitting material, e.g., polymethylmethacrylate (PMMA) or quartz.

Next, the coating is stripped from the end of a fiber, an appropriateadhesive (e.g., UV-curable or fast-curing epoxy) injected into theconnector base, the stripped fiber end inserted through the base intothe glass cylinder, and pushed forward until the fiber end emerges fromthe free end face of the cylinder and the coated fiber extends into theconnector base. After curing of the adhesive, the protruding piece offiber is removed (e.g., by scribing and breaking) and the fiber endpolished flush with the base, for instance, by polishing on 8 μm,followed by 1 μm, polishing paper. After similarly preparing a secondassembly, the connector can be completed by inserting both assembliesinto an alignment sleeve, with or without index matching material (e.g.,silicone gel) between the opposing end faces, and inserting thecombination into a mounting clip.

An assembled exemplary inventive connector is shown in partial cutawayview in FIG. 4. Coated optical fiber 40 is inserted into connector base32, preferably as far as insertion cone 42, with bare optical fiber 41extending through glass cylinder 10. Adhesive is introduced into thebase through bore 34. The assembled connector can be mounted on a solidobject 43, e.g., a wall, by means of mounting clip 31.

Some of the adhesive introduced into the connector base is typicallydrawn into the bore of the glass cylinder, where its presence appears tohave a dynamic centering effect when the fiber is inserted into thebore. In order to take advantage of this centering effect, as well asfor other reasons, it is advantageous to choose the bore diameter andfiber diameters such that the fiber slides relatively easily into thebore, e.g., to result in a fit typically no tighter than a sliding fit.Typically, this means that the bore diameter 2a preferably exceed thediameter of the bare optical fiber by at least about 0.5 μm, butpreferably by not more than about 5 μm.

In addition to the above-discussed exemplary embodiment of theinvention, a wide variety of other embodiments exists, and those skilledin the art will undoubtedly produce still further variants. Forinstance, additional hardware can be added to the basic above-describedconnector to result in twist-lock or screw-in connectors of the typefamiliar for coaxial cable connection, or to provide for stress reliefby means of a metal sleeve crimped to the coated fiber.

An example of a panel-mountable twist-and-lock type connector (i.e., aconnector adapted for feeding a fiber channel through a panel or, moregenerally, a part of a solid object), is shown in FIG. 5. A single fibercable 40 is held fixed in cable retainer and connector base 32, with thebare glass fiber inserted into drawn glass capillary cylinder 10 andextending therethrough, the capillary cylinder being maintained in fixedrelation with respect to 32 by, e.g., adhesive means. The bare fiber andthe cable are also typically maintained in fixed relation with respectto 10 and 32, respectively, by adhesive means. The above-describedcable-terminating assembly is inserted into cap 51 and retained thereinby means of retaining rings 56 and 52, with spring 54, acting againstwasher 55, providing axial force for maintaining the free end faces ofglass cylinders 10 firmly in contact in the assembled connector. Panelmount 57 is typically affixed to a panel or the like by means of screwsextending through openings 58. Into 57's central bore is insertedalignment sleeve 30, and maintained therein by sleeve retainer 50.

As can be seen from FIG. 5, the two cable-terminating assemblies to bejoined are very similar, the major difference between them being thefact that only one assembly comprises spring 54, spacer 59 taking itsplace in the second assembly. It will be appreciated that an inventiveconnector of the type exemplified by FIG. 5 could be constructed to becompletely symmetrical, or to differ in symmetry to a greater extentthan the exemplary depicted embodiment.

To complete the cable connection, one of the glass cylinders, e.g., theone forming part of the "left-hand" assembly of FIG. 5, is inserted intosleeve 30, and the left-hand assembly is attached to 57 by means of thetwist-and-lock arrangement depicted. Subsequently the right-hand glasscylinder is inserted into 30, and the assembly secured as above, withspring 54 not only serving to maintain the glass cylinder end facespressed against each other but also providing locking compression on thetwo twist-and-lock connections of the connector assembly.

FIG. 6 shows experimentally obtained data on connector loss as afunction of capillary cylinder end face separation. As can be seen, theinsertion loss is a strong function of end face separation in aconnector according to the invention, attenuation in db increasingtypically linearly with the logarithm of the separation above someseparation, in the exemplary data, above about 0.4 mm separation.

This phenomenon can be used advantageously to construct a variableattenuator, exemplified in FIG. 7. Buffered coated fibers 40 aremaintained in connector base 32, the bare fiber ends inserted into glasscapillary cylinders 10, and the cylinders inserted into alignment sleeve30, substantially as described above. The connector assembly is mountedin micrometer jaws 71 and 72, held in place by means of set screws 73,the distance between the jaws being controllably variable by means ofmicrometer 70, with rod-and-spring assembly 74 serving to eliminate playin the movement. FIG. 7 is intended to illustrate, by means of a simpleand workable embodiment, the principle of a variable attenuatoraccording to the invention. Those skilled in the art will be readilyable to devise other embodiments of the invention, based on theprinciples disclosed herein.

Other variations of the inventive connector exist. For instance, opticalfilter material can be placed between the opposing end faces of the twoglass cylinders, either in the basic connector assembly (exemplified inFIG. 4), in other connector configurations (e.g., as exemplified in FIG.5), or in adaptations of the invention, e.g., as the variable attenuatorexemplified in FIG. 7. Such a filter could be used to improve thespectral purity of a signal, or to isolate a signal in awavelength-multiplexed optical communication system.

A further embodiment of the inventive connector, namely, a 1×2fiber-to-fiber switch, is depicted schematically in FIG. 8. Connectorbases 32a and 32b are mounted in switch housing 43, and base 32c ismovably held inside the housing. Capillary cylinders 10 are attached tothe bases, coated fibers 40 mounted, and bared fiber ends prepared, asdescribed above. Base 32c is mounted in link 80, part of a 4-barmechanism (further comprising bars 81 and 82, and pins 83-86) attachedto the switch housing. This arrangement allows insertion of the movingcapillary cylinder 10 either into alignment sleeve 30a or 30b. Means forattaching the 4-bar mechanism to the housing, means for maintaining theappropriate axial relation between the abutting capillary cylinders,means for activating switch movement, and the like, can be conventionaland are not shown.

Furthermore, it will be appreciated that, although the discussion aboveis in terms of single-channel connectors, the invention can be embodiedin multi-channel connectors, e.g., by means of multiplicity ofconnectors mounted in a common frame, or plug and socket.

As is apparent from the above description, connectors according to theinvention utilized mechanical means, e.g., an alignment sleeve, formaintaining the two capillary glass cylinders in radially fixed relationto each other, with the outer cylinder surfaces being the alignmentreference surfaces. In other words, the mechanical means are adapted formaintaining the outer cylinder surface of a first cylinder substantiallyconcentric with the outer cylinder surface of a second similar cylinder.This method of alignment precludes radial adjustment of one cylinderagainst the other, to thereby maximize the transmitted signal strength,as is common practice in many prior art single mode connectors, and wedo not contemplate connectors that employ such radial adjustment to bewithin the scope of our invention. However, the disclosed method ofalignment permits rotation of one cylinder with respect to the other,and connectors that allow for such fiber alignment are contemplated tobe within the scope of the invention.

In particular, such rotational alignment is particularly advantageous insingle mode fiber connectors according to the invention. We havefabricated such connectors (of construction substantially as shown inFIG. 4) that utilize "matched" pairs of capillary cylinders, i.e.,cylinders that were adjacent each other in the drawn glass capillarytube, and have obtained connections having very low insertion losses,often below 0.1 db. Of course, if cylinders have sufficiently loweccentricity are available, use of matched pairs may not be necessary.

It will be understood that, after rotational adjustment, it may bedesirable to fix the cylinders in their relative relationship, and anymeans for doing this, including adhesive means, are contemplated to bewithin the scope of this invention.

We claim:
 1. A connector for radiation-transmissively connecting an endof an optical fiber to an end of another optical fiber, said connectorcomprising two fiber termination means, each fiber termination meanscomprising(a) a basically cylindrical plug including an end face inwhich an associated fiber is to terminate, and a passageway whichterminates in said end face and which is adapted to receive an uncoatedend portion of the associated optical fiber that is to be terminated bysaid plug; (b) base means for holding an end portion of the plug andcomprising an axial bore which is aligned with the passageway of theplug in a direction along a longitudinal axis of said connector; atleast one fiber termination means further comprising (c) spring meansdisposed about said base means; (d) cap means for enclosing at least aportion of said base means and said spring means; (e) confinement meansadapted for causing the spring means to urge the base means and theassociated plug in a generally longitudinal direction with respect tothe cap means; the connector further comprising (f) an alignment sleeveadapted to contactingly receive at least an end portion of each of saidtwo plugs in a manner to cause the passageways to be aligned generallyin a longitudinal direction; and (g) housing means for holding saidalignment sleeve and comprising means for securing the two fibertermination means to the housing means such that the end faces of theplugs are maintained in radiation-transmissive relationship.
 2. Theconnector of claim 1, wherein the housing means and the cap meanscomprise mating twist-and-lock means, with the spring means adapted forproviding locking compression on the twist-and-lock means.
 3. Theconnector of claim 1, wherein the spring means comprise a spiral springthat rests against a lip in the cap means and also rests against springretaining means secured to the base means, and wherein the connectorcomprises means, secured to the base means, for retaining the base meansin the cap means.
 4. The connector of claim 1, wherein the passageway isof essentially uniform diameter throughout the length of the plug, butnot excluding the optional presence of an entry cone and/or of achamfer.
 5. A connector for radiation-transmissively connecting an endof an optical fiber to an end of another optical fiber, said connectorcomprising two fiber termination means, each fiber termination meanscomprising(a) a basically cylindrical plug including an end face inwhich an associated fiber is to terminate, and a passageway whichterminates in said end face and which is adapted to receive an uncoatedend portion of the associated optical fiber that is to be terminated bysaid plug; (b) base means for holding an end portion of the plug andcomprising an axial bore which is aligned with the passageway of theplug in a direction along a longitudinal axis of said connector, atleast one fiber termination means further comprising (c) spring meansdisposed about said base means; (d) cap means for enclosing at least aportion of said base means and said spring means; (e) confinement meansadapted for causing the spring means to urge the base means and theassociated plug in a generally longitudinal direction with respect tothe cap means; the connector further comprising (f) an alignment sleeveadapted to contactingly receive at least an end portion of each of saidtwo plugs in a manner to cause the passageways to be aligned generallyin a longitudinal direction; and (g) housing means for holding saidalignment sleeve and comprising means for securing the two fibertermination means to the housing means such that the end faces of theplugs are maintained in radiation-transmissive relationship.
 6. Theconnector of claim 5, wherein the housing means and the cap meanscomprise mating twist-and-lock means, with the spring means adapted forproviding locking compression on the twist-and-lock means.
 7. Theconnector of claim 5, wherein the spring means comprise a spiral springthat rests against a lip in the cap means and also rests against springretaining means secured to the base means, and wherein the connectorcomprises means secured to the base means, for retaining the base meansin the cap means.
 8. The connector of claim 5, wherein the coatedportion is to be maintained in the bore of the base means by adhesivemeans.
 9. An article for terminating an optical fiber comprising(a) abasically cylindrical plug comprising an end face in which an associatedfiber is to terminate, and a passageway which terminates in said endface and which is adapted to receive an uncoated end portion of theassociated fiber; (b) base means for holding an end portion of the plugand comprising an axial bore which is aligned with the passageway in adirection along a longitudinal axis of the article; (c) first meansdisposed about said base means; (d) cap means for enclosing at least aportion of said base means and said first means; and (e) confinementmeans adapted for confining the first means in a longitudinal direction.10. The article of claim 9, wherein the first means are spring means,and wherein the confinement means are adapted for causing the springmeans to urge the base means and the associated plug in the generallylongitudinal direction with respect to the cap means.
 11. The article ofclaim 9, wherein the first means are spacer means.
 12. The article ofclaim 9, wherein the passageway is of essentially uniform diameterthroughout the length of the plug, but not excluding the optionalpresence of an entry cone and/or of a chamfer.
 13. A terminated opticalfiber which comprises an optical fiber end portion and an article forterminating the optical fiber, the article for terminating the opticalfiber comprising(a) a basically cylindrical plug comprising an end facein which the associated fiber terminates, and a passageway whichterminates in said end face and in which an uncoated end portion of theassociated fiber is maintained; (b) base means for holding an endportion of the plug and comprising an axial bore which is aligned withthe passageway in a direction along a longitudinal axis of the article;(c) first means disposed about said base means; (d) cap means forenclosing at least a portion of said base means and said first means;and (e) confinement means adapted for confining the first means in alongitudinal direction.
 14. The terminated optical fiber of claim 13,wherein the first means are spring means, and wherein the confinementmeans are adapted for causing the spring means to urge the base meansand the associated plug in the generally longitudinal direction withrespect to the cap means.
 15. The terminated optical fiber of claim 13wherein the first means are spacer means.
 16. The terminated opticalfiber of claim 13, wherein the passageway is of essentially uniformdiameter throughout the length of the plug, but not excluding theoptional presence of an entry cone and/or of a chamfer.
 17. An articlefor terminating an optical fiber comprising(a) a basically cylindricalplug comprising an end face in which an associated fiber is toterminate, and a passageway which terminates in said end face and whichis adapted to receive an uncoated end portion of the associated fiber;(b) base means for holding an end portion of the plug and comprising anaxial bore which is aligned with the passageway in a direction along alongitudinal axis of the article; (c) first means disposed about saidbase means; (d) cap means for enclosing at least a portion of said basemeans and said first means; and (e) confinement means adapted forconfining the first means in a longitudinal direction, wherein (f) thebase means are adapted for receiving a coated portion of the associatedfiber.
 18. The article of claim 17, wherein the first means are springmeans, and wherein the confinement means are adapted for causing thespring means to urge the base means and the associated plug in thegenerally longitudinal direction with respect to the cap means.
 19. Thearticle of claim 17, wherein the first means are spacer means.
 20. Thearticle of claim 17, wherein the coated portion is to be maintained inthe bore of the base means by adhesive means.
 21. A terminated opticalfiber which comprises an optical fiber end portion and an article forterminating the optical fiber, the article for terminating the opticalfiber comprising(a) a basically cylindrical plug comprising an end facein which the associated fiber terminates, and a passageway whichterminates in said end face and in which an uncoated end portion of theassociated fiber is maintained; (b) base means for holding an endportion of the plug and comprising an axial bore which is aligned withthe passageway in a direction along a longitudinal axis of the article;(c) first means disposed about said base means; (d) cap means forenclosing at least a portion of said base means and said first means;and (e) confinement means adapted for confining the first means in alongitudinal direction, wherein; (f) the base means are adapted forreceiving a coated portion of the associated fiber.
 22. The terminatedoptical fiber of claim 21, wherein the first means are spring means, andwherein the confinement means are adapted for causing the spring meansto urge the base means and the associated plug in the generallylongitudinal direction with respect to the cap means.
 23. The terminatedoptical fiber of claim 21, wherein the first means are spacer means. 24.The terminated optical fiber of claim 21, wherein the coated portion ismaintained in the bore of the base means by adhesive means.